title: Unwinding of the Escherichia coli origin of replication (oriC) can occur in the absence of initiation proteins but is stabilized by DnaA and histone-like proteins IHF or HU.
abstract: The unwinding of the origin of replication (oriC) is a critical step in initiation of DNA replication in Escherichia coli. Previous observations indicate that efficient unwinding of supercoiled plasmid templates containing oriC sequences requires the DnaA initiation protein and one or more accessory factors. The precise contribution of each protein to this process is unknown. Here, we demonstrate that unwinding can occur under physiological conditions at the same bases in oriC, in either the presence or the absence of initiation proteins, as detected by a single-strand specific nuclease, P1. This suggests that oriC unwinding is a spontaneous event determined solely by DNA sequence. DnaA and IHF, as part of a large nucleoprotein complex, may function to stabilize the DNA strand opening prior to initiation of DNA replication.
authors.affiliation: Braun Laboratories 147-75, California Institute of Technology, Pasadena 91125, USA.
authors.forename: P
authors.initials: P
authors.lastname: Polaczek
authors.forename: K
authors.initials: K
authors.lastname: Kwan
authors.forename: J L
authors.initials: JL
authors.lastname: Campbell
mesh_terms: D000225:Adenine; D001426:Bacterial Proteins / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D034982:Integration Host Factors; D010957:Plasmids; D018741:Replication Origin; D013936:Thymidine
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D034982:Integration Host Factors; C040330:histone-like protein HU, bacteria; D000225:Adenine; D013936:Thymidine